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DIY Ghetto idler mounted to ISCG tabs?

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11/9/2021 7:25 AM
Edited Date/Time: 11/9/2021 10:23 AM

Sup bike nerds!
Wanted to start this thread to pick some brains about high pivots. A team mate of mine has a Kona Process X and complained to me about pedal kickback when riding chunky terrain. Since it is a linkage activated single pivot, the suspension kinematics are impacted by pedal force. The hub he is using doesn't have that high of engagement so Im not worried about that affecting things. Being the mechanic that wants to make bikes faster, I started down the wormhole of trying to reduce the kickback he was feeling.
My thinking is that raising the chain to be at or above the pivot point will reduce the amount of resistance he feels when the suspension compresses.
To achieve this, I am wanting to design a DIY idler that mounts to the ISCG-05 chain guide mounts.

EDIT*
Pedal Kickback might not be the correct term for the sensation the rider is feeling. In his explanation, he described a fighting feeling coming from the cranks while descending a pretty chunky trail here in Pisgah.
Going back to basic geometry, taking the 'Triangle' shape of the drivetrain and adding another solid point would essentially create a parallelogram where the lengths of the sides would stay the same.
While not being as drastic of a change, we've got some downtime this offseason and want something to keep us occupied.

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Making bikes go fast since 2020

11/9/2021 7:55 AM

rad question and idea. stoked to see some feedback

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11/9/2021 8:14 AM
Edited Date/Time: 11/9/2021 8:23 AM

I though this was going to be about lan's A cheaper high pivot idler pulley thread. Some good stuff there. I think the main issue would be supporting the piece under loads. ISCG 05 is meant for chain retention which allows the mounts to be so low because all they have to do is act in tension if the chain tries to jump off. With all of that chain tension you'd want to tie into another point on the frame at a point at or higher than the pulley to stabilize the unit. Not all designs will allow for this. I'm not very familiar with the Kona...

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11/9/2021 8:35 AM
Edited Date/Time: 11/9/2021 8:35 AM

I thought the process X had pretty low amounts of pedal kickback?

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11/9/2021 8:36 AM

Big Bird wrote:

I though this was going to be about lan's A cheaper high pivot idler pulley thread. Some good stuff there. I think the main ...more

Right. That’s my worry too. However, some chain guides have a different idler under the chainring to hold the chain on. While it is not subject to as much force, it still has to deal with a good amount of tension.

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Making bikes go fast since 2020

11/9/2021 8:37 AM

The Process X seems to have a particulary low main pivot already. Is he using a very small chainring?
Kickback should be below average even though it is a single pivot. You can calculate critical speed above which you would not encounter any kickback at all (angular velocity of the rear wheel equals angular velocity of the hub).
I suspect the Kona to be in the 10kp/h range, so i wouldn´t bother compromising pedaling performance.

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11/9/2021 8:41 AM

Krafkloot wrote:

The Process X seems to have a particulary low main pivot already. Is he using a very small chainring?
Kickback should be below ...more

The bike does not really matter. I just included it as a starting point for the idea. It’s the off-season now so we are wanting to do some tinkering.
An add on idler would also be cool for some bikes like the Marin wolf ridge which had an insane amount of pedal feedback.

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Making bikes go fast since 2020

11/9/2021 8:43 AM

Don't let team robot see this.

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11/9/2021 9:37 AM

Doing that will greatly affect (lower!) the antisquat characteristics of the bike. To put it directly, it will bob to the moon and back.

Like Big Bird mentioned, if you are going to make it, make it _THICC_. Billet aluminium, as thick as it can be between the tab and the chainring, fill any space between the chainring and the frame/swingarm, etc. The bike is carbon and doesn't have many useable bolts close by (shock mounts and/or pivots), so it will be hard to use any of those.

The main differentiator in the above point is the main pivot. Honestly it appears to be fairly low for both single pivot and quite a few FSR applications, so I'm kind of surprised pedal kickback is the main issue here (I'd say it should be somewhat low compared to some other bikes, same goes for antisquat values). And adding an idler will thus make it squat HARD (even more so than I originally anticipated).

But still, if it needs to be done, how is the main pivot constructed? Is there a spacer between the swingarm and the bearing? Where is the bearing? Is it possible to sandwich an additional blade like part between the swingarm and the blade to provide additional support? Sadly Kona doesn't provide any technical drawings/manual (cycling industry SERIOUSLY needs to rethink some of the practices... Geez!) so I can only imagine how the swingarm is mounted. If you have any closeup (disassembled would be better!) pics of the pivot, that would also help.

But, honestly, I would advise against doing something like this, unless you have the machines, time and knowledge to whip it up quickly and cheaply just to test it out. Unless something weird happens with physics, the bike should pedal horribly with an added idler.

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11/9/2021 9:47 AM

Primoz is correct. An idler in this application is not the proper solution to the pedal kick problem. An idler will have too many negative affects on the rest of the kinematics to make it worth it. There are a few companies that currently have solutions for this; WRP CentreHub, O-chain and a few others. I would recommend either of those to try first.

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11/9/2021 9:54 AM
Edited Date/Time: 11/9/2021 10:08 AM

Thank you for the input everyone. I know its a bad idea, thats the main driving factor behind building something.
While I agree that it is not the most ideal solution to any problem, seeing the rise of the high pivot in DH racing has sparked my, and my team mate's interest in testing something out.
We aren't concerned with pedaling dynamics such as the anti-squat. Regardless of suspension design or gear selection, we just thought it would be a cool idea to come up with something that could possibly affect the way the bike rides.

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Making bikes go fast since 2020

11/9/2021 10:01 AM

I'd also like to clarify something with regard to the title of this thread "DIY Ghetto High Pivot Idler" as well as the home page head line "Is a DIY High-Pivot Conversion Using ISCG05 Tabs Possible?" To the general consumer these titles are misleading. An idler and high pivot suspension design do, in general, accompany each other. But a bicycle with an idler does not make it a high pivot as an idler is independent of the pivot placement.

I understand the "high pivot" is a buzz word right now (doing it for the clicks), but the bummer is that title doesn't even address the main concern of the writer, "how can I reduce pedal kick back? Is an idler the answer?"

All this does is create more confusion in the industry and it doesn't help the consumer.

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11/9/2021 10:05 AM

Yeah, wanted to add basically the same thing after reading the 'high pivot in DH racing' part. To need an idler in a bike you also need a high pivot point, either virtual (multilink system) or actual (single pivot system). Like I mentioned, not only does the Process X not have a high pivot point, I'd say (eyeballing it) that it's lower than a lot of the competition in the 'normal pivot height' class of bikes. Let alone the high pivot ones.

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11/9/2021 10:11 AM

chasewarner2 wrote:

I'd also like to clarify something with regard to the title of this thread "DIY Ghetto High Pivot Idler" as well as the home ...more

Awesome point chase! I changed the title of the thread

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Making bikes go fast since 2020

11/9/2021 11:21 AM

Could it be that he's not feeling pedal kickback, but brake jack from a single pivot, that then extends/stiffens the rear, which is felt harshly through the feet?
Quick test is to do a chainless and normal run.

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11/9/2021 4:57 PM

The process X appears to have very low pedal kickback and neutral brake effects so I would be considering other changes too.

How is the chain length and clutch condition? If the chain is too long or it runs down the block in smaller cogs with the pulley right back then the lower section of chain will be pulling on the cranks too.

If you do go ahead with the idler make it all burley as hell, and the larger diameter/higher tooth count the better. Also take care where you place it to get the desired change. A more shallow turn around the pulley will put less load on it, so in general I would think the further back you can put it the better too as it will make everything much easier

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11/9/2021 9:23 PM

Or further forward and brace it to the shock bolt. Antisquat will be falling rapidly through travel in that case, but with the idler far back the chain might even lift off it deep into travel.

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11/9/2021 11:49 PM

It's possible that the effects he is feeling are due to braking/dragging brakes, which does inherently affect the suspension on a single pivot design more than most others. Maybe a floating brake mount is what is actually needed?

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11/10/2021 5:50 AM
Edited Date/Time: 11/10/2021 7:50 AM

The most likely affect is in his head wink - If kids on tiktok are literally coming down with tics after watching too many Tourettes videos, I think its fair to suggest we mountain bikers are often feeling things just because the "internet told us so".

No matter how good your suspension is, you are going to feel feedback through your feet. Until we create hover crafts, that is just how it works.

EDIT: So you can read it.

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11/10/2021 6:19 AM

jeff.brines wrote:

The most likely affect is in his head wink - If kids on tiktok are literally coming down with tics after watching too many ...more

I had a awakening when i rode a last generation Orange Patriot for some months. A 180mm singlepivot with no fancy anything which is supposed to ride like crap. The perfect combination of all parameters made a bike that was feeling almost magical for my riding style.
A bike is far more than its obvious features and i agree our head is messing with our judgement a lot. So keep tinkering anyhow, whatever everybody is suggesting online. Nothing beats experience you made yourself, on your terrain, with your abilitiy and your riding style. There is no such thing like a perfect bike for everybody.

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11/10/2021 6:46 AM

you tried a big chainring yet? would move the chain up and reduce kickback at the cranks (chaingrowth divided by a larger number of teeth).



I noticed a change for the better swapping a 30T to a 32T on a Commencal Meta AM. Would have been interesting to repeat runs and change from the 30T to a 34T or 36T if it would fit.



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11/10/2021 6:56 AM

chasewarner2 wrote:

I'd also like to clarify something with regard to the title of this thread "DIY Ghetto High Pivot Idler" as well as the home ...more

i made the homepage title and you're right, i just slapped it up there as "high pivot" w/o thinking about it - clearly you can't turn a kona into a high pivot bike by adding an idler. title has been changed on homepage to "DIY idler conversion..."

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11/10/2021 8:45 AM

chasewarner2 wrote:

I'd also like to clarify something with regard to the title of this thread "DIY Ghetto High Pivot Idler" as well as the home ...more

sspomer wrote:

i made the homepage title and you're right, i just slapped it up there as "high pivot" w/o thinking about it - clearly you ...more

Thanks Spomer, much appreciated!

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11/10/2021 10:11 AM
Edited Date/Time: 11/10/2021 10:36 AM

It sounds like you're asking lots of good questions and I love that you're not afraid of tinkering. I'm sure the sensation your friend is feeling in his feet is real, but I'm also certain it isn't pedal kickback he's feeling on his Process X.

If I had to wager, I'd say the feeling in his feet is definitely caused by... something. His fork could be too soft and he's shifting weight onto his feet, it could be because his compression is too firm or too soft, his rear shock could be too stiff or too soft, it could be because his feet are tired, or his tires could be too low in pressure. It could be a lot of things. If it were me, I'd start with suspension setup and body position, and I'd recommend video taping your friend through that same section of trail to diagnose if something looks visibly out of whack. Video can be incredibly helpful for these things.

Also worth reiterating that idler pulleys are subjected to ENORMOUS amounts of torque from pedaling. Big Bird alluded to this when he mentioned finding an additional mounting point for the idler backplate, and Primoz alluded to this when he recommended making that plate THICC. All of your pedaling torque is transferred through an idler pulley, essentially pulling it down as you pedal. Chainguide pulleys and thin aluminum chainguide plates simply don't see this kind of torque because the chain is slack on the bottom side of the chainring and not under load when you're pedaling. The only time chainguide plates and ISCG tabs see that level of torque is when you hit a rock with the bashguard, and that often results in catastrophic failure for the part. It's not the sort of force you'd want to inflict on a part every time you pedal. So if you're going to give it a try, I agree with Primoz and Big Bird that you'll want to drastically overbuild it beyond what seems necessary if it's going to be functional.

I shared my extended thoughts on pedal kickback in this Vital article here, concluding that pedal kickback is definitely not a thing you need to worry about: https://www.vitalmtb.com/features/MTB-ADVICE-with-Team-Robot-ANSWERS-2,3031


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11/10/2021 11:02 AM

I believe Vorsprung had a thing on "Pedal Feedback" as well... https://www.pinkbike.com/news/video-does-your-suspension-really-work-better-without-a-chain.html

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11/10/2021 12:29 PM

Dave_Camp wrote:

you tried a big chainring yet? would move the chain up and reduce kickback at the cranks (chaingrowth divided by a larger ...more

I made my Meta AM 36T for bike park season, definitely makes a difference. Also kills your legs when you actually have to pedal uphill lol.

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11/10/2021 2:52 PM

Since I hear it's a single pivot, I'd definitely change the design focus to a floating rear brake set up. It makes a world of difference. My home made DH bike uses a Santa Cruz Bullit swing arm which used to have a floating brake option. I set it up first without it and it rode great because I was used to single pivots. But when I added the floating rear brake it was a whole new world. So amazingly much better.

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11/10/2021 11:44 PM

Big Bird wrote:

Since I hear it's a single pivot, I'd definitely change the design focus to a floating rear brake set up. It makes a world of ...more

have you got a picture of your floating disc brake on your meta?

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11/11/2021 3:54 AM

Take a gusset Lil chap upper chaing guide - the one that clamps to the seat tube, and then use another upper iscg 05 chain guide. Find a pulley from something. Use the Lil chap as an additional brace to support the iscg 05 chain guide as close to your pulley as possible, I would probably try to mount it extended backwards off the seat tube if the other guide can line up with it. Get creative with some bolts, washers, maybe a drill bit. Voila. Upper pulley that is supported well enough.

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11/11/2021 4:36 AM

The Kona has a square seat tube and is carbon. No bueno.

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